Numerical and calendar calculations for provisions of the German Civil Code ('Buergerliches Gesetzbuch', BGB) < https://www.gesetze-im-internet.de/bgb/>. Covers time limits ('Fristen'), interest ('Zinsen'), monetary limits ('Betragsgrenzen'), proportional allocations ('Quoten') and inheritance calculations ('Erbrecht'). German parameter names preserve statutory terminology ('deutsche Rechtsbegriffe'). Results include exact fractions ('Brueche'), calculation steps ('Rechenschritte'), assumptions ('Annahmen') and a fixed source identifier ('Quellenfassung'). Legal conditions require qualified inputs. Conditional models require justified method choices ('Methodenwahl'); universal legal completeness is not asserted ('keine umfassende Rechtsentscheidung').